1. Field of the Invention
The invention relates generally to socket and pin electrical connectors and, more specifically, to low-insertion force connectors of the type.
2. Description of the Prior Art
In the prior art, the tubular electrical socket contact with split tines is familiar and has been widely employed. Ordinarily, the process of manufacturing the individual socket members, a plurality of which may be included in a multi-connection electrical connector, have been manufactured by processes including a step of bending or deforming the tines in a radially inward fashion. This constricts the aperture of the socket to an effective diameter less than that of the pin such that when a mating pin is inserted therein, a substantial frictional gripping force is exerted against it. Usually, there is some flaring of the tines outwardly at the aperture or, in other cases, a small amount of countersink is put into the insulating body block holding the socket connector members to provide some guidance, compensating for slight pin misalignments as the connectors are mated.
Typical prior art sockets are extensively described in the technical and patent literature, for example, in U.S. Pat. No. 3,286,222 and in the drawings of U.S. Pat. No. 3,043,925. The socket members in those patents are of the crimped or bent-tine types. Those conventional socket contacts exhibit several sensitive parameters that adversely effect the achievability of repeatable, low insertion force while maintaining satisfactory contact pressure. Those areas of concern are: the modulus of elasticity (or Young's modulus) of the material; length of the beam (considering the tines as cantilevered beams); the moment of inertia of the beam representing the tines (governed by socket outside diameter, inside diameter and slot width); beam deflection called for by the design; and, finally, frictional characteristics of the pins within the sockets.
Forces resisting the mating of the pin and socket are essentially frictional forces arising from the socket tines, producing a normal force; i.e., a frictional force, on the pin. These forces, applied by the socket tines, are more thoroughly analyzed hereinafter. Suffice it to say at this point in the description, that a particular minimum amount of normal force is necessary to assure proper electric conduction. Normal forces in excess of this minimum, however, contribute little to electric conduction but still increase the insertion forces.
In the manufacture of the individual socket members according to prior art methods, the crimping or bending of the tines radially inward produces plastic (inelastic) deformation of the tines at their roots; i.e., adjacent to the inward extremity of the slots which are cut in to produce the tines themselves from the tubular body of the material. Not only does this operation result in work-hardening of the material in the root area, it does so in a relatively unpredictable fashion and nonuniformly with respect to the inside and outside fibers of the tine roots, these being subjected to compressive and tensile deformation, respectively.
Since the pin-gripping force achievable, according to the aforementioned prior art manufacturing method, is highly variable; therefore, in order to insure the least minimum pin-gripping force for all connections, overdesign in that respect is the usual approach. Thus, particularly in the connector assembly involving the substantial number of socket members, the overall insertion force can be quite large.
The manner in which the invention overcomes the disadvantages of the prior art by providing a unique socket structure, manufactured in accordance with a novel process, will be understood as this description proceeds.